Machine-switching telephone-exchange system



A. E. LUNDELL.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JUNE 7, I9I5.

Patented Apr. 20, 1920.

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MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JUNE 7, 1915.

Patented Apr. 20, 1920.

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A. E. LUNDELL.

APPLICATION FILED JUNE 7. I9I5.

Patented Apr. 20, 1920.

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MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

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UNITED STATES PATENT OFFICE.

AIlBEN E. LUNDELL. or NEW YORK. a. Y., 'AssIeNoR, BY. ransnnnssxenmmrrs, To WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION or NEW YORK.

MACHINE-SWITCHING TELEPHONE-EXCHIANGE SYSTEM.

Specification of Letters Patent. Patented Apr, 20, 1920.

Application filed June 7, 1915. Serial No. 32,618.

of New York, have invented certain new and useful Improvements in lVIachine-Switching Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to a telephone exchange system having both manual offices and oflices employing machine switching.

Its object is to provide for the transfer of a call from a manual office to a semiautomatic. oilice, and the novelty consists in a circuit arrangement whereby a call orlginating in a manual office is'trunked therefrom to a semi-automatic oflice and is there extended over automatic selector switches under control of-an operator, the sender of such operator being automatically disconnected from the said automatic switches the instant the connector is set upon the wanted line. In case the line is busy, automatic means is brought into play at the connector to operate a visual signal before the manual or originating operator to inform her of this fact, whereupon she so informs-the calling subscriber. Preferably this visual signal is the regular supervisory lamp associated wlth the calling plug of the manual .operators cord circuit, and the automatic means at the connector may consist of an electromagnetic device which causes the supervisory relay -Fig. 3 is a diagram of the connector and associated apparatus.

The cord circuit, shown in Fig. 1, is well known in the art, and therefore need not be described in detail. ceiver by-the calling party at substation A in initiating a call causes the line lamp LL of such line to be lighted at the operators position.- In response to the illumination swering supervisory relay SR closing a of this lamp the operator inserts the plug P in the jack J and inquires the number of the wanted party, the energization of the anshunt circuit about the answering supervisory lamp SL to prevent its illumination in The removal of the rethe well-known manner. Upon ascertaining that the desired number belongs to a subscriber whose line terminatesin a semiautomatic oflice, she communicates over an order wire (not shown) with an operator at such semi-automatic ofiice, which operator we will hereinafter term the B operator.

This operator will then assign a trunk teri minating in a jack "J, to be used by the subscribers operator or A operator, as she will hereinafter be called, and depresses the key 203 of the connecting circuit belonging to the trunk so assigned. The B operator is provided with a number of senders, an idle one of which is adapted to be automatically associated with the connecting circuit (Figs. 2 and 3) of her position, to which the depressed key 203 belongs, upon the depression of such key. She then writes down the number of the'wanted line upon her keyboard, which registers this number. After the number has been registered by the sender, the keyboard is freed therefrom, and the sender begins its operation of controlling the automatic switches of Figs. 2and 3. This sending equipment is temporarily associated with the connecting circuit by the leads 236, 212, 207, 208 and 205. For thesake of simplicity, the sending apparatus is not shown, since it is fully disclosed in Patent No. 1,168,319 of January 18, 1916.

The invention will be more readily apparent from a detailed description of the operations involved in setting up a call between substation A; Fig. 1, terminating in a manual office, and substation B2, 3, terminating in a semi-automatic oflicef The removalv of the receiver by the'calling party at substation A closes the following circuit to light the line lamp LL: free pole of battery, left winding of line relay LR, left armature and back contact of cut-off relay CO, line conductor a, the telephonic apparatus at substation A, lineconductor I). inner armature and back contact of cutoff relay CO, right winding of relay LR, to battery. The line relay at its'armature and front contact closes the circuit of line lamp IL. The operator upon observing the illumination of the lamp LL inserts the answering plug P into the answering jack J of the calling line, and depresses her listeningkey LK and inquires the number of the wanted party, the cut-off relay being operated in-the usual way to open the circuit of the line relay LR and cause the extin guishment of the line lamp LL. The energization of the supervisory relay SR shunts out the supervisory lamp SL of the calling party in the well-known manner. Upon learning the number wanted, which will be assumed to terminate in a connector in a semi-automatic ofiice, the answering or A operator communicates, by means iof an order wire in the well-known manner, with a B. operator at such office who is' provided with a sender by means of which" she can direct automatic switching apparatus to connect with the desired hue. This operator, which will be called the cordless or B operator, informs the A operator over the order Wire'of the trunk to be used. The A operator thereupon inserts the plug P into the jack J of such trunk. In the meantime, the B operator depresses key 203 to movethe sequence switch 200 to prepare circuits for causing one of her senders to be.

key 203 closes the following circuit to move sequence switch S to position 2: free pole of the battery, sequence switch motor magthe driving circuit of the cord finder switch.

net 200, conductor 265,- sequence switch spring 201 (1), conductor 202, key 203 to ground. The numbers adjacent the sequence switch contacts "indicate the closed positions thereof, they being open in all other positions. The contact spring A, however, is a special contact to insure the full movement of the sequence switch to the next intended stopping position, and the numbers near it indicate the positions wherein this contact is open, it being closed in all the positions not noted.

The sequence switch tables at the left of Fig. 2 and in the upper left-hand corner of Fig. 3 aid in tracing the circuits. In position 2 of sequence switch S the closure of spring 204 by grounding conductor 205 moves the sender sequence switch into position 2, and the closure of spring 206 bottom grounds conductor 207 which terminates in a fixed contact of the cord finder switch as fully disclosed in said patent. The sender sequence switch in position 2 closes the driving circuitof this cord finder switch, and when one of its brushes reaches the said grounded contact connected to conductor 207, the test relay of the cord finder is energized and at its back contact opens and thus associates the sender with the trunk. This relay in energizing locks itself to conductor 208 and sequence switch contact 206 (2-9) which is grounded at sprin 204 and contact 232. It may be mentlone atthis point that contact 232 permanently grounds spring 204. The sequence switch-S now waits in position 2 until the operator has written down the number upon the key-board and the sender has recorded such number. When the sender has recorded such number, the sequence switch controlling the same advances and closes a circuit to control the first selecting operation. This circuit will be referred to hereafter as the fundamental circuit. It leads as follows: free pole of the battery, right winding of control relay (3R, conductor 210, spring 211 (2), conductor 212, through the stepping relay,

sender, to ground. The relay C at its left armature and front contact and spring 267 (2) advances the sequence switch S to position 3 to close the circuit of driving magnet P of the selector S, and at its right armature and front contact locks itself directly to conductor 212 over the following path: free pole of the battery, right winding ofrelay CR, its armature and front contact, conductor 223, sprinIg 229, spring 213 (2), to conductor 212. he circuit for magnet P is as follows: free pole of battery, conductor 216, magnet P, conductor 218, spring 219 (3), conductor 231, left armature and front contact of relay CR, to ground. The magnet P in attracting its armature 220 forces the brush shaft 221 into engagement with the constantly rotating driving shaft 222. The selector switch need not be described in detail herein since it is fully described in the patent referredto. The stepping relay at the sender is intermittently operated as the shaft, 221 moves upwardly and operates a series of counting relays 'atthe sender which, in conjunction with the set condition of the sender, measures off the extent of travel of the shaft.

lVhen a predetermined number of such counting relays has operated, determined by a contact, closed in the sender by the operator in writing down on her keyboard the called number, a cut-off relay is operated to open the fundamental circuit just traced, the consequent deenergization of control relay CR opening the circuit of power control magnet I to stop the elevating movement of the shaft 221, which is held elevated in any suitable manner. Considering the operation more in detail, for each contact of the commutator A? passed over, the following circuit is closed in shunt of the stepping relay at the sender spring 229 (3), conductor 224, contacts of the segment" A, brush 226, spring 293 (3) to ground. Assuming that the first brush is the one to be selected, as the brush 226 passes over the first A interrupter segment, the cut-off relay at the at the.

senderoperates, which results in the deinergizationof control relay OR. The control relay by openingits left armature and front contact opens the circuit. of magnet P whereupon motion, of the shaft 221 is ar rested. When the brush shaft stops, it is in such a position that the operation of the; trip magnet TM will release only the first set of brushes 6, b, '6 upon the continued sender preliminary eration." When this circuit is. complete the control relay GRis again energized and at its left armature and front gcontact' and spring 267 moves the sequence switch to position 5, and at its right armature and front contact locks itself'tov conductor 212 which leads to the stepping relay at the sender as before. The clrcuit ofnmagnet l is again closed by way of spring 219 (5).

- and the left armature and front contact of control relay CR. The shaft 221 1s thereupon elevated. During the beginning of its movement, the trip magnet M trips the selected set of brushes.- For each segment of the B commutator passed over, the step- 204, conductor 260, spring 259 (7), conducping relay at the sender is shunted by way of spring 213 (5) and conductor253. We will assume that the trunks leadin to the desired group of final connectors is t e third group in the division of the panel served bythe selected set of-brushes. Therefore, upon the third operation of the stepping relay, due to its being shunted by the brush 227 and B commutator segments, conductor 253, spring 213 (5), the cut-off relay at the sender opens the fundamental circuit, resulting in deenergizing the relay GR. The relay CR at its left armature and front contact opens the circuit of magnet P with the test brush in contact with a terminal grounded by conductor't below the selected group of trunks, and at its back contact moves the sequence switch to position 6 over the following circuit: free pole of the battery, magnet 200, conductors 265, 266,

228, spring 227 (5), left armature and back contact of relay CR, to ground. Due to the closure of spring 211 (.6), the relay GR immediately pulls up again and locks itself up to such terminal 21 over the following circuit: free gple of the battery, right winding of relay 1 ,7 right armature and front contact, conductor 223, spring 229 (6), conductors 230, 257 brush b, to grounded test terminal t At its left armatureand front contact, relay GR moves the sequence switch to position 7. In this position the magnet P is energized over the following circuit to elevate the-shaft 221: free pole of the hat conductnr' 290, segments .test terminal .22 indicated ductors 258, 257 to tery, conductor 216, magnet P, conductor 218, spring-219 (7), conductor 231, left armature and front contact of relay OR, to ground. .As the brush 5 niinals t the control relay is holdup over the following .circuit:'free.pd1e of battery, spring 251 (7), left'windingof said rela of commutator L, brush 225, spring 294 (7), conductors 291, 231, armature and front contact of relay C R to ground} 'When' the brush b reaches of an idle trunk,iwhich is lay GR fa back when, the brushes 6, b have been accurately: A centered thereon, whichoccurs; when the brush 225 passes off the segment of the commutator G corresponding'thereto. The circuit of ma et P is thus opened at the left armature an front contact of relay CR to stop the switch. This relay at its back contact and spring 227 (7) drives the sequence. switch S from position 7 to position 9. The brushes 6, b are now connected to terminals '25, t, leading to the final'selector or connector having access'to tor 292, right armature and back contact of relay R, conductor 223, spring 229 (7), conductors 230, 257, to test brush 6 As the sequence switch moves-into position 8,

passes between ter- 1yl the absence of ground, the res this ground leads over the circuit ust traced to spring 259 (8), from thence over cons'aid test brush.

During thetrunk hunting operation just described, the sender was Waiting for the sequence switch S to reach position 9. The fundamental circuit in position 9 is again closed to control the selection of the brush at the connector. Assuming that the number, of the-wanted line is 455 and that each connector has a capacity of 500 lines, it-' Will be necessary g has access to-the lines from 400 to 499. The fundamental circuit to the connector is as follows: free pole of the battery (Fig. 3),

to trip the fifth brush which relay CR, conductor 311, spring 346 (1),

conductor 315, conductor 347, terminal t, brush Z), conductor 255, spring 233. (9') con ductors 262, 256, 212, through the stepping relay at the sender, to ground. The relay C'R immediately locks itself up directly to the conductor 315 by way of conductor 3.14, armature and front contact -of said relay and-spring 313 (1). At itsright'armature and front contact, relay C R closes the following circuit to move the sequence switch S of the connector-into position 2: free pole of the battery, magnet 300, conductors 303, 304, spring 305 1), conductors 306, 307, conductor 308 right armature and front contact of relay 67R, to ground. In position 2. trunk relay 335 is energized over a circuit by way of spring 348 (2) and locks itself over the following cir'carit: free pole of the battery, relay 335, left armature and front contact thereof, conductor 302, spring 301 (2), conductor 380, terminal t brush b conductors 257, 258, spring 259 (9). conductor 260, to grounded spring204.

The relay 335 at its right armature and l'rontcontact moves the sequence swltch S to position 3 by way of sprlng 349 In position 3 the high speed magnet H is energized and by attracting its armature 376 forces the brush shaft 350 against the constantly rotating shaft 377. This circuit is as follows: free pole of the batter magnet 'l-l, conductor 309, spring 310 (3 conductors 307, .308, right armature and front contact of relay CR, to ground. Each time the brush 321 contacts with a segment of commutator A, the stepping relay at the sender is shunted by the closure of the following path for the current: spring 233 (9), conductors 262, 234, spring 235 (9), conductor 263, brush b, terminal t, conductors 351, 319, spring 318 (3), conductor- 320, segments of commutator A', brush 321 to ground. Upon the engagement of brush 321 with the fifth A segment, and consequently upon the fifth deenergization of the stepping relay at the sender, the cut-off relay thereat is operated to open the fundamental circuit. This results in the deenergization of relay C R which at its right armature' and back contact conductor 332 and spring 316 (3), moves the sequence switch S to position 4. In position 4, the trip magnet TM is energized over conductor 337 and spring 336 circuit is again closed at the sender, the relay C'R is again energized and locks up to conductor 315 over the circuit previously traced. At its armature and front contact and spring 305 (4) it moves the sequence switch 8 to position 5. In position 5 the circuit of magnet H is again completed as follows: free pole of the battery, magnet H, conductor 309, spring 310 (5), conductor 307, conductor 308, right armature, and front contact of relay CR, to ground. For each segment of the tens commutator B passed over, the stepping relay at the sender is shunted over the circuit previously traced to spring 318, but instead of passing by way of conductor 320 and brush 321 to ground, now passes by way of conductor 323, commutator B and brush 322, to ground. Upon six operations of the stepping relay, the number assumed being 455, the cut-off relay at the sender opens the fundamental circuit which results in the denergization of the relay CR. The falling back of the right armature of this relay When the fundamental quence switch S from position 5 to 6. When the fundamental circuit-is again closed at the sender, the relay G'R' is again energized and locks up over the circuit previously traced. The closure of the right armature and front contact of relay C'R moves the sequence switch S from position 6 t0 positi0n7 over the following circuit: free pole of the battery, magnet 300, conductors 303, 304, spring 305 (6), conductors 306, 307, 308, ri ht armature and front contact. of relay Cat, to ground. In osition 7, the circuit of low speedmagnet J is closed, and in attracting its armature 377 forces shaft 359 into engagement with the constantly rotating shaft 378. This circuit is as follows: free pole of the battery, magnet L, conductor 317, spring 310 (7) conductors 307, 308, ri ht armature and frontcontact of relay C to ground. Each time the brush 321 engages a segment of commutator C", the stepping relay at the sender is shunted over the circuit previously traced up to the spring 318, from thence it continues by way of conductor. 320, segments of commutator C, brush 321, to ground. When the stepping relay at the sender has operated six times, the units digit of the called number being 5, the sender operates the cut-off relay which opens the fundamental circuit, which results in the denergization of relay CR' which at its right armature and front contact opens the circuit of magnet L to. stop the elevating movement of the shaft 350 in engagement with the line 455 selected. The sender at the end of units selection causes its sequence switch to 200 of the sequence switch S (Fig. 2) over conductor 236 and spring 201 (9), whereupon the sequence switch moves to position 10. In passing out of position 9 spring 206 by opening its upper contact causes the release of the sending apparatus.

The A operator is assumed at this time to have inserted plug P into jack J (Fig. 1) thus causing the energization of relay 264 2), which at its front contact closes the following circuit to move the sequence switch S from position 10 to position 11: free pole of the battery, magnet advance and close a circuit for the magnet 200, conductors 265, 266, spring 267 (10),

conductors 268, 246, 239, armature and front 'of the relay C'R (Fig. 3) at the end of units selection moves the sequence switch S from posltion 7 to position 8 over the to ground.

following circuit: free pole of the battery,

"magnet 300, conductors 303, 304, spring 316 relayTR (Fig. 3) is now connected to test brush 6 over the following circuit: free pole of'the battery, spring 324 (8), both windings of test relay TR, conductor 328, spring 330 (8), conductor 331, test brush 7).

If the line is busy, this test relay will not receive enough current for its energization due to the closure of a similar circuit in shunt of it at the other connector connected to this line, or due to the presence of an answering plug similar to P (Fig. 1) in the answering jack of such subscriber. Therefore the relay TR will not pull up its armatures. In position 8, the relay CR is energized over the following circuit: free pole of the battery, relay CR, conductor 311, spring 346 (8), conductors 353, 351, terminal 25, brush 7), conductor 263, spring 235 (11), conductor 269, right armature and back contact of relay 247, conductor 243, left armature and front contact of relay 244 to ground. This relay was energized over the following circuit when the A operator inserted plug P into jack J and energized relay 264: free pole of the battery, relay 244, conductors 245, 246, 239, armature and front contact of relay 264, conductor 240, spring 268, to grounded spring 204. Relay CR at its right armature and front contact moves the sequence switch S to position 10 over the following circuit: free pole of the battery, magnet 300, conductors 303, 304, spring 305 (8), conductor 306, 307., 308, armature and front contact of relay C'R, l/Vhen the connector sequence switch arrives in position 9, the following circuit is closed to energize the relay 334: free pole of the battery, conductor 354, relay 334, conductor 355, spring 330 (9), conductor 331, brush b terminal 25 through the cut-off relay of the selected line, to

ground. This relay locks itself over conductor 356, spring 340 (9), its armature and grounded spring 341. In moving out of po-. sition 8, sequence switch S opened the circuit just traced for relay CR' at spring 346 (8). Its right armature in retracting, closes the segment Y. the following circuit is closed to drlve the sequence switch fromj position 11 to position 16: free pole of the battery, magnet 300, conductors 303, 304, spring 316 (11), conductor 342, segment Y, brush 322, to ground. Spring 316 being closed to conductor 342 in position 16 also, the sequence switch S immediately moves into position 17. In position 17 the interrupter 343 intermittently closes a circuit to relay GR by way of spring 344 (17) and conductor 311. The relay (1' l at its right armature and front contact applies ground to conductor 347 through the resistance 345. The intermittent application of this ground to conductor 347 causes the relay 248 (Fig. 2) to open and close its front contact to close a shunt around the lefthand high resistance winding H of relay 264, which in turn so increases the flow of current in the circuit leading back to the A operators position that the calling supervisory relay SR is intermittently energized to flash the calling supervisory lamp SL. This indicates to the A operator that the line desired is busy, whereupon she so informs the calling party. Considering this operation more in detail, relay 237 was energized in parallel with relay 244 over the following path: free pole of battery, relay 237, conductor 361, lefthand armature and back contact of relay 247, armature and back contact of relay 242, conductors 238, 239, armature and front contact of relay 264, conductor 240, spring 268 (11) to ground at spring 204.

The first application of ground to conductor 347 energizes the relay 242 (Fig. 2) over the following circuit: ground, right armature and front contact of relay CR (Fig. 3), conductor 308, resistance 345, spring 360 (17), conductor 347, terminal 2 brush conductor 255, spring 233 (11), conductor 271, armature and front contact of relay 237, marginal ringing relay 242, ,ringing generator 280, to ground. The re- ,,lay 242 opens the short circuit about relay 247 which is energized over the following circuit: free pole of the battery, relay 237. conductor 361, relay 247, conductors 238, 239, armature and front contact of relay 264, conductor 240, spring 268 (11), to ground at spring 204. Relay 247, by attracting its armature, short-circuits relay 237, which in falling back connects together conductors 270 and 271. The intermittent energization of the relay CR' (Fig. thus intermittently grounds conductor 347 and operates the relay 248 intermittently, which at its armature and front contact shunts out the left high resistance winding II of relay 264, thus increasing the current in the circuit of calling supervisory relay SR (Fig. 1) which causes the lamp SL to flash, thus indicating that the called line is busy. The A operator will thereupon inform the calling party of this fact and withdraw, plugs I and I from the jacks J and J.

The withdrawal of plug P from jack J causes the deenergization of relay 264 (Fig. 2). The retraction of the armature of relay 264 causes the deenergization of relay 244. The interrupter I intermittently connects ground to the right-hand armature of relay 244. Therefore when the relay 244 is de-v of battery, right winding of relay CR, conductor 210, spring 272 (12) which closes its lower contact before opening its upper contact, interrupter II to ground, until interrupter II breaks its contact which occurs about a second after interrupter I breaks its contact, these two interrupters being mounted on the same shaft. The relay CR then falls back and at its left armature and back contact and spring 227 (12) moves the sequence switch to position 13. When interrupter I again closes its contact it energizes relay CR over the circuit previously traced, which relay at its left front contact and spring 267 (13) moves the sequence switch to position 15. Due to the de'e'nergized condition of relay 244, the sequence switch moves directly out of position 15 and into 17 over the following circuit: free pole of the battery, magnet 200, conductors 265, 274, spring 275 (15), conductor 282, left armature and back contact of relay 244, to ground. In position 17 a circuit is closed for the return magnet R to restore the brush shaft 221. This circuit is as follows: free pole of the battery, magnet R, conductor 276, spring 259 (17), conductor 260, to ground at spring 204. The magnet R by attracting its armature 277 forces the shaft 221 into engagement with the constantly rotating shaft 278 which drives the shaft downwardly. When the brush 227 contacts with segment Y, the following circuit is closed to drive the sequence switch to normal position: ground, spring 293 (17) brush 227', segment Y, conductor 279, spring 227 (17), conductors 228, 266, 265, magnets 200. to battery. Vvhen the sequence switch S left position 14, the locking circuit of trunk relay..335 (Fig. 3) was opened at spring 259 (Fig. 2). This relay at its right armature and back contact and spring 349 (17 closes a circuit to drive sequence switch S from position 17 into position 18. Due to the brush 322 engaging segment Y. the follow ing circuit is immediately closed to drive the sequence switch to normal position grounded brush 322, segment Y, conductor 342, spring 316 (18), conductors 304, 303, mag net 300, to battery. The apparatus is now restored ready for use with another call.

S from position 7 to lposition 8. If the J line be idle, the relay R will become energized since it is not shunted by a connection to a multiple thereof at another connector or answering plug. The relay TR immediately locks itself up to the cut-oifrelay of the selected line at its right armature and front contact and conductor 380, and at its left armature and front contact moves the sequence switch out of position 8 over the following circuit: free pole of the battery, magnet 300, conductors 303, 304, spring 305 (8), conductor 352, left armature and front contact of relay TR, conductor 333, to ground at spring 341. The sequence switch immediately moves out of position 10, due to the deenergized condition of relay C'R, the circuit being as follows: free pole of the battery, magnet 300, conductors 303, 304,

spring 316 (10), conductor 332, right armature and back contact of relay CR to cuit: free pole of the battery, magnet 300,

conductors 303, 304, spring 305 (11), conductor 352, left armature and front contact of relay TR, conductor 333, to grounded spring 341, and into position 16 under the. control of the contact A closed between these positions in the manner well understood. When the sequence switch arrives in position 16, the selected line is signaled over the following circuit: ringing generator 280 (Fig.2), marginal relay 242., armature and front contact of relay 237, conductor 271, spring 233 (11), conductor 255, brush 7), terminal 15, conductor 347, spring 360 (16), conductor 363, brush N, terminal 6', line conductor 7), bell 364, condenser 365. line conductor a, terminal t, brush 7), conductor 366, spring 367 (16). conductor 351, terminal 2?, brush 7), conductor 263, spring 235 (11), conductor 260, right armature and back contact of relay 247, conductor 243, left armature and front contact of relay 244, to ground. The bell 364 is intermittently operated in the well-known manner. When the subscriber at substation B removes his receiver and closes a shunt about the condenser 365 and bell 364, the relay 242 which is marginal is energized in the well-known manner, and by opening its back contact removes the short circuit about relay 247.

' has answered.

This relay by attractingits left-hand armature shunts the relay 237, which in retracting its armature opens the ringing circuit and closes connection between talklng conductors 270 and 271. The relay 247 at its party from the battery over the windings of repeating coil R. The relay 248 is included in the talking circuit and energizes when the called party responds. In closing its armature and front contact it shunts out the high resistance windin H of relay 264 which causes the relay- CR (Fig. 1) to be energized to extinguish the lamp SL indicating to the A operator that the called party Current is fed to the calling party from the battery over the windings of repeating coil B (Fig. 1). The subscribers may now converse.

Upon the hanging up of the receiver by the calling party'at substation A, the supervisory relay SR is deenergized and causes the lamp SL to light in the wellknown manner. The A operator thereupon withdraws the plugs P and I from the jacks J and J. respectively. The removal of the plug P from the jack J causes the deenergization of relay 264 (Fig. 2). This relay in retractin its armature deener izesthe relay 244. fihen the interrupter next grounds the right armature of relay 244, the relay GR is energized over the following circuit: free ole of the battery, right winding of relay lR, conductor 210, spring 272 (11 conductor 250, to the right grounded armature conductor 214, left armature and front conof relay 2 44. The relay CR at its left armature and front contact closes the following I circuit to move the sequence switch S to position 12: free pole of the battery, magnet 200, conductors 265, 266, spring 267 ('11);

tact of relay CR, to ground. In position 12 relay CR is held energized over the circuit:

free pole of the battery, right winding of relay CR, conductor 210, spring 272 (12) interrupter II to ground, until interrupter l II breaks its contact. The relay CR then falls back and at its left armature and back contact and spring 227 .(12) moves the sequence switch to position 13. hen interrupter I again closes its contact it energizes relay (ll over the circuit previously-traced,

.which relay at its left front contact moves the sequence switch to position 15. Due to the deenergized condition of relay 244, the closure of the following circuit moves the sequence switch directly out of position 15 and into position 17 free pole of the battery, magnet 200, conductor 265, conductor 274, sprin 275 (15), conductor 282, to ground at t 1e left armature and back contact of relay 244. In position 17, a circuit is closed to drive the shaft 221 to normal position as follows: free pole of the battery, magnet R, conductor 276, spring 259 (17), conductor 260, to ground at spring 204. When the brush 227 reaches the segment Y,

the following circuit is closed to drive the I sequence switch to normal position: free pole of the battery, magnet 200, conductors 265, 266, 228, spring 227 (17) conductor 279, segment Y, to grounded brush 227. The sequence switchS and the selector S are thus restored to normal position.

When the sequence switch left position 14 spring 259 opened the locking circuit for trunk relay 335 at the connector (Fig. 3). This relay in retracting its right armature drives the sequence switch from position 16 1nto position 18 over the following circuit: free pole of the battery, magnet 300, conductor 303, spring 349- (16, 17), conductor 368, right armature and back contact of relay 335, .to ground. In' position 18 a circuit is closed to drive the connector brush shaft to normal position as follows: free pole of the battery, return magnet R, conductor 338, spring 348 (18), to ground. NVhen the brush 322 in its return movement reaches the segment Y, the following circuit is closed to drive the sequence switch to normal position: grounded brush 322, segment Y, conductor 342, spring 316 (18), conductors 304, 303, magnet 300, to battery. Both the connector and v the connector sequence switch S are now restored to normal position.

In order to keep the B operator informed lector S and the connector C are operating to connect with'thewanted line, and that the sequence switch S in moving out of position 9 by the opening of the engagement between spring 206 and its upper contacts, releases the sender at the end of units selection. 'Thus the lamp L intermittently flashes as long as the connection is being established and remains lighted continuously as soon as the connector is set upon the terminals of the selected line. Thus,.-if for any reason the switches are not properl set, the continued flashin of the lamp;

:- operatorv then withdraws the plug. P from the jack J. The withdrawal of the plugwill indicate this fact to the operator. 7

If, for any reason, the shaft 2210f "the group switch S fails- 'tol.becomedisengaged from the driving shaft- 221, it will, uponreaching se mentjX', close the following circuit for t e sequence switch magnet 200: free -pole of the battery, magnet- 200, ,COHE ductors 265, 274, spring 286 (1 to 8 inclusive), conductor 287, segment X, to

brushes 226,227, spring 293, to ground. The

sequence switch is thus moved into position 9. Inthis position alamp 288 is lighted over the following circuit: free pole of the battery, lamp 288, spring 286 (9), conductor 287, segment X, grounded brush 226. This,

lamp is preferably located on the racks which carry the switches. The lighting of this lamp will indicate to an attendant thatthe switch has failed to operate properly, and the continued flashing of the lamp L will-indicate this fact to the B operator, who

will then assign another trunk to the A operator: Similarly in the connector if the brush shaft 350 is not arrested before the brushes 321, 322 reach the segmentX, the following circuit is closed to drive the sequence switch into position 16: free pole.- of the battery magnet 300, conductors 303, 304, 377, 372, spring 373, conductor 374,

segment X, to grounded brushes 321, 322. The sequence switch in position 16 closes the following circuit to light the lamp 375; free' pole of the battery, lamp 375, conductor" 376, ggring 373 (16), conductor 374, segment to grounded brushes 321, 322. The lighting of this lamp will indicate to an attendant that the switch has failed to act properly.

If the group switch S in position 7 fails to find an idle trunk, the test brush 7) in leaving the last test terminal of the group opens the locking circuit of relay CR. This relay at its left armature andback contact opens the circuit of magnet P, thus stopping the switch. The closure .of its left armature to its back contact moves the sequence switch out of position 7 into position 9. When the brush 7) leaves the test terminal t of the last trunk line in the group, the brush .226 engages a segment of the commutator Z. This results in the closure of the following circuit for the sequence switch S to drive the same into position 15: free pole of the battery, magnet 200, conductors 265, 266, 228, spring 227 (9 to 13), conductor 224, segment Z, brush 226, spring 293 (9). In this position a circuit is closed to cause the lamp L to flash. This circuit is as follows: free pole of the battery, lamp L,'spring 284 (15), interrupter-IV to ground. This interrupter may be constructed differently from interrupter III, This signal will indicate to the operator that all the trunksare busy; She may then communicate this fact to the A operator over the order wire which deenergiz es the relay 244 whose circuit is controlled-at a front contact of. relay 264.

The relay 244 at its left armature and back contact closes the following circuit'to drive the sequence switch S into position 17, in which the brush shaft 221 is restored: free 221 is as follows: free pol of the battery,

magnet R, conductor 276, spring 259 (17), conductor 260, to grounded spring 204. WVhenthe grounded brush 227 reaches the segment Y, the following circuit is closed to drive the sequence switch from position 17 e to normal: free pole of the battery, magnet 200, conductors, 265,266, 228, spring 227 (17) conductor 279, segment Y, to grounded brush 227.

. A lamp 283 is provided for each connecting circuit and becomes-illuminated when the A operator plugs into the jack J thereof, provided the operator has not depressed the key 203 to move the sequence switch S to position 2. Thus, if the A operator inserts a plug into the wrong jack, the B operator will be made aware of it in this manner. This lamp would also be illuminated in case the sequence switch S fails to completely restore after the A operator Withdraws the plug P from the jack J, thus decnergizing relay 244, and by its continuous illumination serves as an indication of the failure of the apparatus to function properly.

What is claimed is:

1. In a telephone exchange system, the combination with a manual board, calling subscribers lines terminating in jacks therein, a cord circuit having an answering and a calling plug, a calling supervisory lamp associated with said cord circuit, a semiautomatic board, trunk circuits consisting of two wires only, said trunk circuits terminating at one end in jacks at said manual board and at the other end in selectors at said semi-automatic board, connectors at said called line to cause said supervisory lamp to flash intermittently. I

2. In a telephone exchange system, the combination with a manual board, calling subscribers lines terminating in jacks therein, a cord circuit having an answering and a calling plug, a supervisory lamp and relay controlling the same associated with said cord circuit, a semi-automatic board, link circuits consisting of two wires only, said link circuits terminating at one end in jacks at said manual board and at the other end in selectors at said se1niauto1natic board, connectors at said se1ni-automatic board, called lines terminating therein, means for setting said connectors on called lines, means whereby the said lamp is lighted upon the connection of the calling plug to a trunk jack, means for energizing said supervisory relay opera-ted if the called subscriber responds to render said signal inert, and means actuated by the busy condition of the called line for restoring the connector and for intermittently opera-ting said supervisory relay to cause said supervisory lamp to flasha a 3. In a telephone exchange system, the combination with a manual board, calling subscribers lines terminating in jacks therein, a cord circuit having an answering and a calling plug, a telephone set adapted to be connected to said cord, a supervisory sig nal and a relay adapted to operate the same associated with said cord circuit, a semiautomatic board, link circuits terminating at one end in jacks in said manual board and at the other end in selectors at said semiautomatic board, connectors at said semiautomatic board, called lines terminating in said connectors, a relay at said semi-automatic board having a high resistance winding in circuit with said supervisory relay, a relay at the semi-automatic board controlling a shunt about said high resistance winding, means for intermittently operating said relay if the called line is busy to cause the said supervisory relay at the manual board to operate said signal intermittently.

4. In a telephone exchange system, the combination with a manual board, calling subscribers lines terminating in jacks therein, a cord circuit having an answering and a calling plug, a telephone set adapted to be connected to said cord, a supervisory lamp and a relay adapted to shunt the same associated with said cord circuit, a semiautomatic board, link circuits terminating at one end in acks in said manual board and at the other end in selectors at said semiautomatic board, connectors at said semiautomatic board, called lines terminating in said connectors, means for setting said connectors on said lines, means whereby the said lamp is lighted upon theconnection of the calling plug to a trunk jack, means for restoring the connector if the called line is busy, a relay at said semi-automatic board having a high resistance winding in circuit with said supervisory relay, a relay at the semi-automatic board controlling a shunt about said high resistance winding, means for intermittently operating said relay if the called line is busy to cause the said supervisory relay at the manual board to flash said lamp.

5. In a telephone exchange system, the

combination with amanual board, calling subscribers lines terminating in jacks therein, a cord circuit having an answering and a calling-plug, a telephone set adapted to be connected to said cord, a supervisory lamp and a relay adapted to shunt the same associated with said cord circuit, a semi-autom'atic board controlling a shunt about said high resistance winding, means for operatmg said relay when the called party responds to cause said supervisory relay to render said lamp inert, and means for intermittently operating said relay if the called l1ne is busy to cause the sald supervisory relay at the manual board to flash said lamp.

6. In a telephone system, a plurality of subscribers lines, a manual board, means, for establishing a connection between two of said lines including a cord circuit at said board having an answering and a callin plug, a trunk circuit terminating at sai manual board in a. jack adapted to receive said calling plug, an automatic switch, means for connecting said trunk to said switch and for setting the same on the called line, a signal in said cord, means for conductively separating but inductively unit ing said trunk, a bridge across said trunk on the calling side of said means, a relay bridged across said trunk on the called side of said means, means for intermittently operating said last-mentioned relay when the called line is busy, means controlled by said relay for changing the resistance of said calling bridge, and means controlled by such change in resistance for operating said signal.

7. In a telephone exchange system, the combination with a manual board, calling subscribers lines terminating in jacks therein, a cord circuit having an answermg and a calling plug, a supervisory signal and a relay controlling the same associated with said cord circuit, a semi-automatic board, link circuits consisting of two wires only, said link circuits terminating at one end in jacks in said manual board, connectors at said semi-automatic board, means for connecting said trunk to said connectors, called lines terminating at said connectors,- the substations of such lines being provided with switchhooks normally maintaining the telephonic circuits thereat open, means for setting said connectors on called lines, means whereby said supervisorv relay is responsive .with said cordcircuit, a semi-automatic board, link circuits terminating at one end in jacks in said manual board and at the other end 1n selectors 1n said semi-automatic board, connectors at said semi-automatic board, called lines terminating in said connectors, the substations of such lines being provided with switchhooks normally maintaining the telephonic circuits thereat open, means for setting said connectors on said lines, a relay at said semi-automatic board having a high resistance winding in circuit with said supervisory relay, a relay at the semi-automatic board controlling a shunt about said high-resistance winding, interrupters associated with said connectors, said interrupters being adapted intermittently to operate said relay if the called line is busy to close said shunt to cause the said supervisory relay at the manual board to operate said lamp in one manner, and a circuit including the called line and switchhook thereat for operating said relay at the semi-automatic board to cause said signal to operate in another manner.

9. Ina telephone exchange system, the combination of a manual board, calling subscribers lines terminating in jacks therein, a cord circuit having answering and callin plugs, a supervisory signal and a relay a apted to operate the same associated with said cord circuit, a semi-automatic board, link circuits terminating at one end in jacks in said manual board and at the other end in selectors in said semi-automatic board, connectors at said semi-automatic board, interrupters associated therewith, called lines terminating insaid connectors, the substations of such lines being provided with switchhooks normally maintaining the telephonic circuit thereat open,

means for setting said connectors on said lines, a metallic c1rcu1t extendmg between said signal to indicate when a calle said manual and semi-automatic boards and including said supervisory relay, a relay at said semi-automatic board adapted to vary the resistance of said metallic circuit, a circuit-for said relay controlled by the called line switch-hook and a second circuit therefor controlled by said interrupter, and means actuated by the busy condition of the called line for closing the circuit of said relay and interrupter.

10. In a telephone system, called line, an A-operators board, a -operators board, automatic switches, me ns for extending connection from said -operators board to said switches, means for controlling said switches for extending connection to said called line, a si nal at said A-operators board, a relay bridged across the conductors of the talking circuit at said B-operators board, means for intermittently varying the resistanceof said bridge when said automatic switches attempt to make connection with a busy line, and means controlled by the variation of said current f0! intermittently operating saidsignal;

11. In a telephone system, a called line, an A-operators board, a B-operators board, automatic switches, means for extending connection from said A-operators board to said B-operators board and from said B-operators board to said automatic switches, means controlled by said automatic switches for extending connection to the called line, a signal on said A-operators board, a bridge across the conductors of the talking circuit, means for increasing the flow of current through said bridge when said automatic switches attempt to make 12. In a telephone system, a called line,

an A-operators board, a B-operators board, automatic switches, means for extending connection from said' A-operators board to said B-operators board and from said B-operators board to said automatic switches, means controlled by said automatic switches for extending connection to the called line, a supervisory signal on said A-operators board, means for ope ating subscriber responds and when a disconn ction is desired, a relay bridged across the conductors of the talking circuit at said B-operators board, means for short-circuiting part of the winding of said relay to thereby reduce the resistance of said bridge when said automatic switches attempt to make connection with a busy line, and means controlled by the change in resistance of said bridge for operating said signal.

In witness whereof, I hereunto subscribe my name this 4th day of June, A. D. 1915.

ALBEN E. LUNDELI: 

